Power recovery device of liquid processing apparatus

ABSTRACT

According to one embodiment, a power recovery device is used in an apparatus in which firstly pressurized raw water (FPRW) is supplied to a reverse osmosis membrane unit to extract fresh water and condensed and depressurized raw water (HPB) remains. The device recovers the energy of HPB, rises a pressure of raw water (LPF) by using the recovered energy, and adds such secondly pressurized raw water (HPF) to the FPRW. The device accommodates a fixed center shaft and a rotary member on the shaft in a housing. LPF flows into one paired chambers of the housing and radial channels of the member to push and rotate the member, and HPB is introduced into the channels through paired openings of the shaft to push out LPF as HPF from the channels and another paired chambers of the housing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of PCT Application No. PCT/JP2010/059220, filed May 31, 2010, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a power recovery device of a liquid processing apparatus.

BACKGROUND

A liquid processing apparatus which processes water containing a plurality of components (to be referred to as raw water hereinafter) by using a reverse osmosis membrane called, e.g., an RO membrane is known.

The raw water is supplied to the reverse osmosis membrane at a high pressure, and fresh water is extracted from the raw water by the reverse osmosis membrane. In this process, a ratio of fresh water extracted by the reverse osmosis membrane rises as a value of the pressure of the raw water supplied to the reverse osmosis membrane rises. To raise the pressure value of the raw water, however, it is necessary to increase a strength of a raw water pressure raising device which is necessary to raise the pressure value of the raw water, and an amount of energy required to increase the pressure of the raw water also increases. In addition, a structure of the raw water pressure raising device is normally complicated.

Raw water from which the fresh water is extracted at a given ratio by the reverse osmosis membrane (to be referred to as high-concentration raw water hereinafter) loses its pressure more or less because the fresh water is extracted by the reverse osmosis membrane. However, the high-concentration raw water maintains most of the high pressure loaded on the raw water when supplied to the reverse osmosis membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing the whole of one example of a liquid processing apparatus in which a power recovery device according to a first embodiment.

FIG. 2 is a perspective view schematically showing an outer appearance of the power recovery device according to the first embodiment.

FIG. 3 is a schematic exploded perspective view of the power recovery device of FIG. 2.

FIG. 4 is a schematic perspective view showing, from below, a case including a center shaft of the power recovery device of FIG. 3.

FIG. 5 is a schematic perspective view showing a horizontal section of a rotary member of the power recovery device of FIG. 3.

FIG. 6 is a schematic perspective view of the center shaft of the power recovery device of FIG. 3.

FIG. 7 is a schematic perspective view of a lower portion of the center shaft of FIG. 6, after the center shaft is cut along a line IIV-IIV.

FIG. 8 is an exploded perspective view similar to FIG. 3, for explaining an operation of the power recovery device of FIG. 2.

FIG. 9 is a schematic plan view of a combination of the case, center shaft, and rotary member of FIG. 8, for explaining the operation of the power recovery device of FIG. 2.

FIG. 10 is a schematic exploded perspective view of a power recovery device according to a second embodiment.

FIG. 11 is a perspective view showing a rotary member of the power recovery device of FIG. 10, with a half of the rotary member being horizontally cut.

FIG. 12 is a perspective view of a center shaft of FIG. 10.

FIG. 13 is a schematic perspective view of a lower portion of the center shaft shown of FIG. 12, after the center shaft is cut along a line XIII-XIII.

FIG. 14 is a schematic perspective view of a lower end part portion of the lower portion of the center shaft of FIG. 13, after the lower portion is further cut along a line XIV-XIV.

DETAILED DESCRIPTION

A power recovery device of a liquid processing apparatus, according to an embodiment is a power recovery device which is used in a liquid processing apparatus in which raw water as externally supplied water containing a plurality of components is supplied to a reverse osmosis membrane through a pressure raising unit and extracts a part of fresh water from the pressure raised raw water by the reverse osmosis membrane, and which supplies raw water a pressure of which is raised by using a pressure of remaining raw water from which the part of the fresh water is extracted by the reverse osmosis membrane to the reverse osmosis membrane, in addition to the pressure raised raw water from the pressure raising unit.

The power recovery device comprises: a housing having an internal space; a center shaft fixed in the internal space of the housing and having an outer circumferential surface and at least one end portion protruding outside the housing; and a rotary member accommodated in the internal space of the housing such that the rotary member is rotatable on the outer circumferential surface of the center shaft, having an inner circumferential surface opposing the outer circumferential surface of the center shaft and an outer circumferential surface positioned outside the center shaft in a radial direction of the center shaft, and including a plurality of channels arranged at equal intervals in a circumferential direction of the center shaft and each extending between the inner circumferential surface thereof and the outer circumferential surface thereof.

At least one set of two pairs of chambers opposing the outer circumferential surface of the rotary member and divided from each other is provided in the internal space of the housing.

At least one set of two pairs of openings opening in the outer circumferential surface of the center shaft to be equal in number to the chambers to oppose the at least one set of the chambers in the internal space of the housing through the rotary member, and at least one set of two pairs of passages extending through the center shaft from the at least one set of the openings and opening in the at least one end portion of the center shaft, are formed in the center shaft.

One pair of the chambers symmetrically arranged with respect to the center shaft in the one set of the chambers in the internal space of the housing is configured to be introduced with the externally supplied raw water and to cause the externally supplied raw water to push the plurality of channels in the outer circumferential surface of the rotary member exposed in the one pair of chambers, in a predetermined circumferential direction of the outer circumferential surface so as to rotate the rotary member.

The other pair of the chambers symmetrically arranged with respect to the center shaft in the one set of the chambers is connected to a channel of the raw water between the pressure raising unit and the reverse osmosis membrane.

One pair of the openings of the one set of the openings in the outer circumferential surface of the center shaft, opposing the one pair of the chambers through the rotary member are communicated with an outside through one pair of the passages corresponding to the one pair of the openings in the center shaft.

The other pair of the openings of the one set of the openings in the outer circumferential surface of the center shaft, opposing the other pair of the chambers through the rotary member is introduced with the remaining raw water through the other pair of the passages corresponding to the other pair of the openings in the center shaft.

First of all, a schematic structure of the whole of an example of a liquid processing apparatus in which a power recovery device according to a first embodiment will be explained with reference to FIG. 1.

The liquid processing apparatus of the example is a seawater desalination apparatus. In this seawater desalination apparatus, raw water as externally supplied water containing a plurality of components is seawater. Seawater SW pumped up from the sea is supplied to a preprocessing unit 10. The preprocessing unit 10 preprocesses the supplied seawater SW by adding, e.g., a germicide 10 a, flocculant 10 b, scale inhibitor 10 c, dechlorine agent 10 d, etc. to the seawater SW. Seawater (preprocessed seawater) PSW which is preprocessed is led to pass through a water supply pump 12 and safety filter 14 by a pipe. The preprocessed seawater PSW passed through the safety filter 14 is branched into two parts by branched pipes.

One branched pipe is connected to a reverse osmosis membrane unit 18 containing a reverse osmosis membrane 18 a through a pressure raising unit 16. In this example, the pressure raising unit 16 is provided by a high-pressure pump. The preprocessed seawater PSW on which a predetermined high pressure is loaded by the pressure raising unit 16 is supplied to the reverse osmosis membrane unit 18 by the one branched pipe. In the reverse osmosis membrane unit 18, the reverse osmosis membrane 18 a extracts a part of water (fresh water) FW from the high-pressure preprocessed seawater HPSW.

The extracted water FW is led to a clear water tank 20 by a pipe. In the clear water tank 20, clear water CW is produced by adding, e.g., a hardness control agent 20 a, pH adjuster 20 b, disinfectant 20 c, etc. to the water FW. The clear water CW produced in the clear water tank 20 is supplied to a water pipe 23 through a clear water supply pump 22.

The other branched pipe is connected to the power recovery device 24 according to the first embodiment.

The low-pressure preprocessed seawater PSW to be supplied to the power recovery device 24 through the other branched pipe is called as low-pressure feed LPF. Seawater (high-concentration seawater) in which concentrations of the various components including salt are increased because a part of the water FW is extracted by the reverse osmosis membrane unit 18 and the pressure is more or less decreased, is led to the power recovery device 24 through a pipe. This high-concentration seawater supplied from the reverse osmosis membrane unit 18 to the power recovery device 24 is called as high-pressure brine HPB.

In the power recovery device 24, a pressure of the high-pressure brine HPB is raised by the energy of the low-pressure feed LPF, and then the high-pressure brine HPB the pressure of which is raised pushes the low-pressure feed LPF and raises a pressure of the low-pressure feed LPF, and finally high-pressure feed HPF is discharged. That is, the energy of the high-pressure feed HPF is generated by using most of the energy of the high-pressure brine HPB, and by adding a part of the energy of the low-pressure feed LPF.

The high-pressure feed HPF is led by a pipe from the power recovery device 24 to a pipe between the pressure raising unit 16 and the reverse osmosis membrane unit 18. In this pipe, the high-pressure feed HPF is added to the high-pressure preprocessed seawater HPSW flowing from the pressure raising unit 16 to the reverse osmosis membrane unit 18, and flows together with the high-pressure preprocessed seawater HPSW toward the reverse osmosis membrane unit 18.

In the power recovery device 24, the low-pressure feed LPF used to raise the pressure of the high-pressure brine HPB becomes the high-pressure feed HPF in a next stage in which the pressure of the low-pressure feed LPF is raised by the high-pressure brine HPB whose pressure is further raised by using a part of the energy of the low-pressure feed LPF. After raising the pressure of the low-pressure feed LPF, the high-pressure brine HPB loses its pressure and is discharged outside as low-pressure brine LPB from the power recovery device 24.

First Embodiment

Next, a structure of the power recovery device 24 of the first embodiment will be explained with reference to FIGS. 2-7.

As shown in FIGS. 2-4, the power recovery device 24 comprises a housing 32 having an internal space 30. In this embodiment, the housing 32 includes a case 32 a having an almost circular recess that provides the internal space 30, and a lid 32 b that liquid-tightly covers one opening of the recess of the case 32 a. The lid 32 b is detachably fixed to the case 32 a by a well-known fixing means (not shown).

The power recovery device 24 further comprises a center shaft 34 fixed in the internal space 30 of the housing 32, and having an outer circumferential surface and at least one end portion protruding outside the housing 32. More specifically, the center shaft 34 is long and narrow, and a portion of its outer circumferential surface is liquid-tightly fixed in a through hole 32 c formed in a center of a bottom surface of the recess of the case 32 a. The One end portion of the center shaft 34 is positioned at one end along a longitudinal central line of the center shaft 34 and protrudes from the through hole 32 c into an external space below the case 32 a. The other end portion of the center shaft 34 is positioned at the other end along the longitudinal central line and protrudes from a through hole 32 d in a center of the lid 32 b into the external space above the lid 32 b.

The power recovery device 24 further comprises a rotary member 36 accommodated in the internal space 30 of the housing 32 so as to be rotatable on the outer circumferential surface of the center shaft 34. The rotary member 36 includes an inner circumferential surface 36 a opposing the outer circumferential surface of the center shaft 34, and an outer circumferential surface 36 b positioned outside in a radial direction of the center shaft 34. As is well shown in FIG. 5, the rotary member 36 further includes a plurality of channels 36 c arranged at equal intervals in a circumferential direction of the center shaft 34 and each extending between the inner circumferential surface 36 a and the outer circumferential surface 36 b.

As is well shown in FIG. 3, at least one set of two pairs of chambers 38 a and 38 b opposing the outer circumferential surface 36 b of the rotary member 36 and divided from each other is provided in the internal space 30 of the housing 32. In this embodiment, one set of two pairs of the chambers 38 a and 38 b is provided.

The low-pressure feed LPF supplied to the power recovery device 24 as shown in FIG. 1 is led, as shown in FIG. 2, into one pair of the chambers 38 a, 38 a symmetrically arranged with respect to the center shaft 34 in the one set of the chambers 38 a and 38 b in the internal space 30 of the housing 32. The one pair of the chambers 38 a, 38 a are configured such that the supplied low-pressure feed LPF flows along the outer circumferential surface 36 b of the rotary member 36, which is exposed in the one pair of the chambers 38 a, 38 a in a predetermined circumferential direction (in FIG. 3, in a counterclockwise direction) of the outer circumferential surface 36 b.

The other paired chambers 38 b, 38 b of the one set of the chambers 38 a and 38 b, symmetrically arranged with respect to the center shaft 34, are connected to the pipe for the high-pressure feed HPF extending from the power recovery device 24 toward the pipe between the pressure raising unit 16 and the reverse osmosis membrane unit 18 as shown in FIGS. 1 and 2.

As is well shown in FIGS. 6 and 7, at least one set of two pairs of openings 40 a and 40 b equal in number to the at least one set of the chambers 38 a and 38 b in the internal space 30 of the housing 32 is formed in the outer circumferential surface of the center shaft 34 so as to oppose the chambers 38 a and 38 b through the rotary member 36. In this embodiment, one set of the two pairs of the openings 40 a and 40 b is formed in the outer circumferential surface of the center shaft 34 so that the openings 40 a and 40 b are arranged at equal intervals in a circumferential direction of the outer circumferential surface.

One pair of passages 42 a, 42 a (see FIG. 7) extends through the center shaft 34 from the one pair of the openings 40 a, 40 a corresponding to the one pair of the chambers 38 a, 38 a in the internal space 30 of the housing 32 to the other end portion of the center shaft 34, which is positioned upwardly in FIG. 6, and the pair of passages 42 a, 42 a is opened at an end surface of the other end portion. As shown in FIGS. 2, 3, and 6, the paired passages 42 a, 42 a can be integrated into one passage 42 a in the center shaft 34 before they reach the other end portion. As shown in FIGS. 1 and 2, the opening of the integrated passage 42 a in the end surface of the other end portion of the center shaft 34 is connected to a pipe for the low-pressure brine LPB, which extends from the power recovery device 24.

Another pair of passages 42 b, 42 b (see FIG. 7) extends through the center shaft 34 from the other pair of the openings 40 b, 40 b corresponding to the other pair of the chambers 38 b, 38 b in the internal space 30 of the housing 32 to the one end portion of the center shaft 34, which is positioned downwardly in FIG. 6, and opens at an end surface of the one end portion. As shown in FIG. 4, the paired passages 42 b, 42 b can be integrated into one passage 42 b in the center shaft 34 before they reach the one end portion. As shown in FIGS. 1 and 2, the opening of the integrated passage 42 b in the end surface of the one end portion of the center shaft 34 is connected to the pipe for the high-pressure brine HPB, which extends from the reverse osmosis membrane unit 18 to the power recovery device 24.

Next, an operation of the power recovery device 24 described above with reference to FIGS. 2-7 will now be explained with reference to FIGS. 8 and 9.

As shown in FIGS. 8 and 9, the high-pressure brine HPB supplied from the reverse osmosis membrane unit 18 shown in FIG. 1 to the power recovery device 24 reaches the paired openings 40 b, 40 b in the outer circumferential surface of the center shaft 34 through the passage 42 b (see FIG. 4) opened in the end surface of the downward one end portion of the center shaft 34 of the power recovery device 24, and flows into several channels 36 c inner ends of which are exposed to the other paired openings 40 b, 40 b among the plurality of channels 36 c of the rotary member 36. Meanwhile, as shown in FIGS. 8 and 9, the low-pressure feed LPF supplied from the preprocessing unit 10 shown in FIG. 1 to the power recovery device 24 through the water supply pump 12 and safety filter 14 flows into the one pair of the chambers 38 a, 38 a of the case 32 a of the housing 32 of the power recovery device 24. The low-pressure feed LPF flowed into the one pair of the chambers 38 a, 38 a pushes parts of the outer circumferential surface of the rotary member 36, which are exposed in the one pair of the chambers 38 a, 38 a, in a predetermined circumferential direction of the outer circumferential surface of the rotary member 36. As a result, the low-pressure feed LPF in the one pair of the chambers 38 a, 38 a flows into several channels 36 c outer ends of which are exposed to the one pair of the chambers 38 a, 38 a among the plurality of channels 36 c of the rotary member 36, and pushes side surfaces of the several channels 36 c. A part of energy of the low-pressure feed LPF is consumed to rotate the rotary member 36 in a predetermined direction R.

As the rotary member 36 rotates, the low-pressure feed LPF in the channels 36 c is held in the channels 36 c between the one pair of the chambers 38 a, 38 a and the other pair of the chambers 38 b, 38 b and between the one pair of the openings 40 a, 40 a and the other pair of the openings 40 b, 40 b of the center shaft 34. When the channels 36 c holding the low-pressure feed LPF oppose the other pair of the chambers 38 b, 38 b and the other pair of the openings 40 b, 40 b of the center shaft 34, the low-pressure feed LPF held in the channels 36 c is pushed out from the channels 36 c into the other pair of the chambers 38 b, 38 b by the high-pressure brine HPB flowed from the other pair of the openings 40 b, 40 b into the channels 36 c holding the low-pressure feed LPF. During this action, the pressure energy of the high-pressure brine HPB flowed from the openings 40 b, 40 b into the channels 36 c is given to the low-pressure feed LPF held in the channels 36 c, so that the low-pressure feed LPF held in the channels 36 becomes the high-pressure feed HPF and is pushed into the other pair of the chambers 38 b, 38 b.

The high-pressure brine HPB flowed into the channels 36 c from the other pair of the openings 40 b, 40 b becomes the low-pressure brine LPB because the high-pressure brine HPB gives its pressure energy to the low-pressure feed LPF in the channels 36 c and its pressure energy is largely decreased or eliminated. After that, further rotation of the rotary member 36 makes the low-pressure brine LPB being held in the channels 36 c between the other pair of the chambers 38 b, 38 b and the one pair of the chambers 38 a, 38 a and between the other pair of the openings 40 b, 40 b and the one pair of the openings 40 a, 40 a of the center shaft 34. And then, when the channels 36 c holding the low-pressure brine LPB oppose the one pair of the chambers 38 a, 38 a and the one pair of the openings 40 a, 40 a of the center shaft 34, the low-pressure feed LPF is flowed from the one pair of the chambers 38 a, 38 a into the channels 36 c holding the low-pressure brine LPB so that the low-pressure brine LPB in the channels 36 c is discharged out from the power recovery device 24 through the one pair of the openings 40 a, 40 a and the one pair of the passages 42 a, 42 a corresponding to the one pair of the openings 40 a, 40 a.

As shown in FIG. 1, the high-pressure feed HPF in the other pair of the chambers 38 b, 38 b is led by the pipe from the power recovery device 24 to the pipe between the pressure raising unit 16 and the reverse osmosis membrane unit 18. In the latter pipe, the high-pressure feed HPF is added to the high-pressure preprocessed seawater HPSW flowing from the pressure raising unit 16 toward the reverse osmosis membrane unit 18, and flows together with the high-pressure preprocessed seawater HPSW toward the reverse osmosis membrane unit 18.

AS a result of this, if an amount of the fresh water FW extracted in the reverse osmosis membrane unit 18 per unit time is constant, it is possible to reduce an amount of the high-pressure preprocessed seawater HPSW to be supplied from the pressure raising unit 16 toward the reverse osmosis membrane unit 18 per unit time. This makes it possible to reduce an amount of energy, i.e., power necessary to operate the seawater desalination apparatus as a kind of the liquid processing apparatus using the power recovery device 24.

In the power recovery device 24 of this embodiment, the one set of the two pairs of the chambers 38 a and 38 b are provided to be divided from each other in the internal space 30 of the case 32 a of the housing 32, and the same low-pressure feed LPF is supplied to the one pair of the cambers 38 a, 38 a symmetrically arranged with respect to the center shaft 34, and at the same time the same high-pressure brine HPB is supplied toward the other pair of the chambers 38 b, 38 b symmetrically arranged with respect to the center shaft 34. Accordingly, a force loaded on the case 32 a of the housing 32 and a force loaded on the rotary member 36 accommodated in the internal space 30 of the case 32 a so as to be rotatable on the outer circumferential surface of the center shaft 34, by the low-pressure feed LPF in the one pair of the chambers 38 a, 38 a, are canceled in the radial direction of the center shaft 34, and also a force loaded on the case 32 a and a force loaded on the rotary member 36, by the high-pressure brine HPB in the other pair of the chambers 38 b, 38 b, are canceled in the radial direction of the center shaft 34.

Further, a mixture of the low-pressure brine LPB and high-pressure brine HPB, entered into a gap between the outer circumferential surface of the center shaft 34 and the inner circumferential surface 36 a of the rotary member 36 functions as a radial dynamic pressure bearing between the outer circumferential surface of the center shaft 34 and the inner circumferential surface 36 a of the rotary member 36 with a rotation of the rotary member 36 on the outer circumferential surface of the center shaft 34. Also, a mixture of the low-pressure feed LPF and high-pressure feed HPF, entered into gaps between the outer circumferential surface 36 b of the rotary member 36 and regions of an inner circumferential surface of the internal space 30 of the case 32 a of the housing 32, the inner circumferential surface of the internal space 30 opposing the outer circumferential surface 36 b of the rotary member 36 and the regions excepting the one set of the two pairs of the chambers 38 a and 38 b, functions as a radial dynamic pressure bearing between the outer circumferential surface 36 b of the rotary member 36 and the above-mentioned regions of the inner circumferential surface of the internal space 30 of the case 32 a of the housing 32 with the rotation of the rotary member 36 on the outer circumferential surface of the center shaft 34.

Therefore, there is no need for an independent radial bearing between the outer circumferential surface of the center shaft 34 and the inner circumferential surface 36 a of the rotary member 36, and it is possible to simplify the structure of the power recovery device 24 of this embodiment and to reduce a manufacturing cost thereof.

More further, a mixture of the low-pressure brine LPB and high-pressure brine HPB and a mixture of the low-pressure feed LPF and high-pressure feed HPF, both mixtures entered into a gap between an inner surface of the lid 32 b of the housing 32 and one side surface of the rotary member 36, which opposes the above-mentioned inner surface, in the internal space 30 of the case 32 a of the housing 32, function as a thrust bearing between the inner surface of the lid 32 b and the one side surface of the rotary member 36 with the rotation of the rotary member 36 on the outer circumferential surface of the center shaft 34. Simultaneously, the mixture of the low-pressure brine LPB and high-pressure brine HPB and the mixture of the low-pressure feed LPF and high-pressure feed HPF, both entered into a gap between the bottom surface of the internal space 30 of the case 32 a of the housing 32 and the other side surface of the rotary member 36, which opposes the above-mentioned bottom surface, in the internal space 30 of the case 32 a of the housing 32, function as a thrust bearing between the bottom surface of the internal space 30 of the case 32 a and the other side surface of the rotary member 36 with the rotation of the rotary member 36 on the outer circumferential surface of the center shaft 34.

Therefore, there is no need for independent thrust bearings between the inner surface of the lid 32 b and the one side surface of the rotary member 36 and between the bottom surface of the internal space 30 of the case 32 a and the other side surface of the rotary member 36, and it is possible to simplify the structure of the power recovery device 24 of this embodiment and to reduce the manufacturing cost thereof.

Second Embodiment

Next, a structure of a power recovery device 24′ according to a second embodiment and being usable in the example of the liquid processing apparatus described above with reference to FIG. 1, instead of the power recovery device 24 of the first embodiment described above with reference to FIGS. 2-9, will be explained with reference to FIGS. 10-14.

As shown in FIGS. 10-14, the power recovery device 24′ comprises a housing 43 having an internal space 41. In this embodiment, the housing 43 includes a case 43 a having an almost circular recess that provides the internal space 41, and a lid 43 b that liquid-tightly covers an opening on one side of the recess of the case 43 a. The lid 43 b is detachably fixed to the case 43 a by a well-known fixing means (not shown).

The power recovery device 24′ comprises a center shaft 44 protruding from a center of the internal space 41 of the housing 43 into an external space above the lid 43 b through a through hole 43 c in a center of the lid 43 b. More specifically, the center shaft 44 is long and narrow, and a portion of its outer circumferential surface is liquid-tightly fixed in the through hole 43 c in the center of the lid 43 b. One end portion of the center shaft 44, which is positioned at one end along a longitudinal central line of the center shaft 44, protrudes from the through hole 43 c of the lid 42 b into the external space above the lid 43 b. The other end portion of the center shaft 44, which is positioned at the other end along the longitudinal central line, is positioned slightly and upwardly away from the center of the bottom surface of the internal space 41 of the housing 43.

The power recovery device 24′ further comprises a rotary member 46 accommodated in the internal space 41 of the housing 43 so as to be rotatable on the outer circumferential surface of the other end portion of the center shaft 44. More specifically, a blind hole 46 a for receiving the other end portion of the center shaft 44 is formed in a center of the rotary member 46. An inner circumferential surface 46 b and bottom surface of the blind hole 46 a relatively rotatably oppose the outer circumferential surface and end surface of the other end portion of the center shaft 44 received in the blind hole 46 a. The rotary member 46 includes an outer circumferential surface 46 c positioned outside the blind hole 46 a in a radial direction thereof, and a plurality of channels 46 d arranged at equal intervals in a circumferential direction of the blind hole 46 a and each extending between the inner circumferential surface 46 b and the outer circumferential surface 46 c as is well shown in FIG. 11. As is well shown in FIG. 10, at least one set of two pairs of chambers 48 a and 48 b opposing the outer circumferential surface 46 c of the rotary member 46 and divided from each other is provided in the internal space 41 of the housing 43. In this embodiment, one set of the two pairs of the chambers 48 a and 48 b is provided.

As shown in FIG. 10, the low-pressure feed LPF supplied to the power recovery device 24 shown in FIG. 1 is supplied to the one pair of the chambers 48 a, 48 a symmetrically arranged with respect to the center shaft 44 among the one set of the chambers 48 a and 48 b in the internal space 41 of the housing 43. The one pair of the chambers 48 a, 48 a are configured to flow the supplied low-pressure feed LPF along the outer circumferential surface 46 c of the rotary member 46 exposed in the one pair of the chambers 48 a, 48 a in a predetermined circumferential direction (in FIG. 10, a counterclockwise direction) of the outer circumferential surface 46 c.

As shown in FIGS. 1 and 10, the other pair of the chambers 48 b, 48 b symmetrically arranged with respect to the center shaft 44 in the one set of the chambers 48 a and 48 b, is connected to the pipe for the high-pressure feed HPF extending from the power recovery device 24′ toward the pipe between the pressure raising unit 16 and reverse osmosis membrane unit 18.

As is well shown in FIGS. 10, and 12-14, at least one set of two pairs of openings 50 a and 50 b equal in number to the at least one set of the chambers 48 a and 48 b in the internal space 41 of the housing 43 is formed in the outer circumferential surface of the other end portion of the center shaft 44 so as to oppose the at least one set of the chambers 48 a and 48 b through the rotary member 46. In this embodiment, one set of the two pairs of the openings 50 a and 50 b is formed in the outer circumferential surface of the other end portion of the center shaft 44 so that the openings 50 a and 50 b are arranged at equal intervals in the circumferential direction of the outer circumferential surface.

One pair of passages 52 a, 52 a (see FIG. 14) extends through the center shaft 44 from the one pair of the openings 50 a corresponding to the one pair of the chambers 48 a in the internal space 41 of the housing 43 to the one end portion of the center shaft 44, which is positioned upward in the center shaft 44. The one pair of the passages 52 a, 52 a is opened in an end surface of the one end portion. As shown in FIGS. 10, 12, and 13, the paired passages 52 a, 52 a can be integrated into one passage 52 a in the center shaft 44 before they reach the one end portion. As shown in FIGS. 1 and 12, the opening of the integrated passage 52 a in the end surface of the one end portion of the center shaft 44 is connected to the pipe for the low-pressure brine LPB, which extends from the power recovery device 24 (in this embodiment, 24′).

Another pair of passages 52 b, 52 b (see FIG. 14) extends through the center shaft 44 from the other pair of the openings 50 b, 50 b corresponding to the other pair of the chambers 48 b, 48 b in the internal space 41 of the housing 43 to the one end portion of the center shaft 44, which is positioned upward in the center shaft 44. The other pair of the passages 52 b, 52 b is opened in the end surface of the one end portion. As shown in FIGS. 10, 12, and 13, the paired passages 52 b can be integrated into one passage 52 b in the center shaft 44 before they reach the one end portion. In this embodiment, the paired passages 52 b, 52 b are integrated into the one passage 52 b to be concentric with the above described one integrated passage 52 a in the end surface of the one end portion of the center shaft 44. As shown in FIGS. 1 and 12, the opening of the integrated passage 52 b in the end surface of the one end portion of the center shaft 44 is connected to the pipe for the high-pressure brine HPB, which extends from the reverse osmosis membrane unit 18 to the power recovery device 24 (in this embodiment, 24′).

A through hole 43 d is formed in a center of a bottom surface of the internal space 41 of the housing 43 (i.e., a bottom surface of the case 42 a) of this embodiment, and an output shaft 54 a of a motor 54 is rotatably and liquid-tightly inserted into the through hole 43 d. This rotatable and liquid-tight insertion of the output shaft 54 a of the motor 54 can be performed by, e.g., interposing a well-known annular sealing member such as an O-ring or oil seal between the inner circumferential surface of the through hole 43 d and the outer circumferential surface of the output shaft 54 a of the motor 54.

A protruding end of the output shaft 54 a of the motor 54 inserted into the through hole 43 d is concentrically fixed to an out side surface a bottom wall of the blind hole 46 a in the center of the rotary member 46 in the internal space 41 of the housing 43.

An operation of the power recovery device 24′ described above with reference to FIGS. 10-14 will now be explained with reference to FIG. 10.

As shown in FIG. 12, the high-pressure brine HPB supplied from the reverse osmosis membrane unit 18 shown in FIG. 1 to the power recovery device 24 (in this embodiment, 24′) reaches the other pair of the openings 50 b, 50 b in the outer circumferential surface of the other end portion of the center shaft 44 through the passage 52 b opened in the end surface of the upwardly one end portion of the center shaft 44 of the power recovery device 24′, and flows into several channels 46 d inner ends of which are exposed to the other pair of the openings 50 b, 50 b, among the plurality of channels 46 d of the rotary member 46. Meanwhile, as shown in FIG. 10, the low-pressure feed LPF supplied from the preprocessing unit 10 shown in FIG. 1 to the power recovery device 24 (in this embodiment, 24′) through the water supply pump 12 and safety filter 14 flows into the one pair of the chambers 48 a, 48 a of the case 43 a of the housing 43 of the power recovery device 24′. The low-pressure feed LPF flowed into the one pair of the chambers 48 a, 48 a pushes parts of the outer circumferential surface of the rotary member 46, which are exposed in the one pair of the chambers 48 a, 48 a, in a predetermined circumferential direction of the outer circumferential surface of the rotary member 46. As a result, the low-pressure feed LPF in the one pair of the chambers 48 a, 48 a flows into several channels 46 d, outer ends of which are exposed in the one pair of the chambers 48 a, 48 a among the plurality of channels 46 d of the rotary member 46, and pushes side surfaces of the several channels 46 d. A part of the energy of the low-pressure feed LPF is consumed to rotate the rotary member 46 in a predetermined direction R.

As the rotary member 46 rotates, the low-pressure feed LPF in the channels 46 d is held in the channels 46 d between the one pair of the chambers 48 a, 48 a and the other pair of the chambers 48 b, 48 b and between the one pair of the openings 50 a, 50 a and the other pair of the openings 50 b, 50 b of the center shaft 44. After that, when the channels 46 d holding the low-pressure feed LPF oppose the other pair of the chambers 48 b, 48 b and the other pair of the openings 50 b, 50 b of the center shaft 44, the low-pressure feed LPF held in the channels 46 d is pushed out from the channels 46 d into the other pair of the chambers 48 b, 48 b by the high-pressure brine HPB flowed from the other pair of the openings 50 b, 50 b into the channels 46 d holding the low-pressure feed LPF. During this action, the pressure energy of the high-pressure brine HPB flowed from the openings 50 b, 50 b into the channels 46 d is given to the low-pressure feed LPF held in the channels 46 d. As a result of this, the low-pressure feed LPF held in the channels 46 d becomes the high-pressure feed HPF and is pushed into the other pair of the chambers 48 b, 48 b.

The high-pressure brine HPB flowed into the channels 46 d from the other pair of the openings 50 b, 50 b gives its pressure energy to the low-pressure feed LPF in the channels 46 d and becomes into the low-pressure brine LPB because the pressure energy of the high-pressure brine HPB is largely decreased or eliminated. After that, further rotation of the rotary member 46 causes the low-pressure brine LPB to be held in the channels 46 d between the other pair of the chambers 48 b and the one pair of the chambers 48 a, 48 a and between the other pair of the openings 50 b, 50 b and the one pair of the openings 50 a, 50 a of the center shaft 44. And, when the channels 46 d holding the low-pressure brine LPB oppose the one pair of the chambers 48 a, 48 a and the one pair of the openings 50 a, 50 a of the center shaft 44, the low-pressure brine LPB held in the channels 46 d is discharged out from the power recovery device 24 (in this embodiment, 24′) through the one pair of the openings 50 a, 50 a and the one pair of the passages 52 a, 52 a corresponding to the one pair of the openings 50 a, 50 a by the low-pressure feed LPF flowed into the passages 46 d from the one pair of the chambers 48 a, 48 a.

As shown in FIGS. 10 and 1, the high-pressure feed HPF in the other pair of the chambers 48 b, 48 b is led through the pipe from the power recovery device 24 (in this embodiment, 24′) to the pipe between the pressure raising unit 16 and the reverse osmosis membrane unit 18. In the latter pipe, the high-pressure feed HPF is added to the high-pressure preprocessed seawater HPSW flowing from the pressure raising unit 16 toward the reverse osmosis membrane unit 18, and flows together with the high-pressure preprocessed seawater HPSW toward the reverse osmosis membrane unit 18.

As a result of this, if an amount of the fresh water FW extracted in the reverse osmosis membrane unit 18 per unit time is constant, it is possible to reduce an amount of the high-pressure preprocessed seawater HPSW to be supplied from the pressure raising unit 16 toward the reverse osmosis membrane unit 18 per unit time. This makes it possible to reduce an amount of the energy, i.e., a power necessary to operate the seawater desalination apparatus as a kind of the liquid processing apparatus using the power recovery device 24 (in this embodiment, 24′).

Note that, in this embodiment, the rotation of the rotary member 46 in the internal space 41 of the housing 43 can be controlled by using the motor 54.

That is, the amount of the energy to be given to the high-pressure feed HPF which is led through the pipe from the power recovery device 24′ of this embodiment to the pipe between the pressure raising unit 16 and the reverse osmosis membrane unit 18, by the rotation of the rotary member 46 of the power recovery device 24′, can be controlled regardless of a value of a rotation force to be given to the rotary member 46 by the low-pressure feed LPF supplied to the power recovery device 24′.

In the power recovery device 24′ of this embodiment, the one set of the two pairs of the chambers 48 a and 48 b are provided to be divided from each other in the internal space 41 of the case 43 a of the housing 43, and the same low-pressure feed LPF is supplied to the one pair of the cambers 48 a, 48 a symmetrically arranged with respect to the center shaft 44, and at the same time the same high-pressure brine HPB is supplied toward the other pair of the chambers 48 b, 48 b symmetrically arranged with respect to the center shaft 34. Accordingly, a force loaded on the case 43 a of the housing 43 and a force loaded on the rotary member 46 accommodated in the internal space 41 of the case 43 a so as to be rotatable on the outer circumferential surface of the center shaft 44, by the low-pressure feed LPF in the one pair of the chambers 48 a, 48 a, are canceled in the radial direction of the center shaft 44, and also a force loaded on the case 43 a and a force loaded on the rotary member 46, by the high-pressure brine HPB in the other pair of the chambers 48 b, 48 b, are canceled in the radial direction of the center shaft 44.

Further, a mixture of the low-pressure brine LPB and high-pressure brine HPB, entered into a gap between the outer circumferential surface of the other end portion of the center shaft 44 and the inner circumferential surface 46 b of the blind hole 46 a of the rotary member 46 functions as a radial dynamic pressure bearing between the outer circumferential surface of the other end portion of the center shaft 44 and the inner circumferential surface 46 b of the blind hole 46 a of the rotary member 46 with a rotation of the rotary member 46 on the outer circumferential surface of the center shaft 44. Also, a mixture of the low-pressure feed LPF and high-pressure feed HPF, entered into gaps between the outer circumferential surface 46 c of the rotary member 46 and regions of an inner circumferential surface of the internal space 41 of the case 43 a of the housing 43, the inner circumferential surface of the internal space 41 opposing the outer circumferential surface 46 c of the rotary member 46 and the regions excepting the one set of the two pairs of the chambers 48 a and 48 b, functions as a radial dynamic pressure bearing between the outer circumferential surface 46 c of the rotary member 46 and the above-mentioned regions of the inner circumferential surface of the internal space 41 of the case 43 a of the housing 43 with the rotation of the rotary member 46 on the outer circumferential surface of the center shaft 44.

Therefore, there is no need for an independent radial bearing between the outer circumferential surface of the other end portion of the center shaft 44 and the inner circumferential surface 46 b of the blind hole 46 a of the rotary member 46, and it is possible to simplify the structure of the power recovery device 24′ of this embodiment and to reduce a manufacturing cost thereof.

More further, a mixture of the low-pressure brine LPB and high-pressure brine HPB and a mixture of the low-pressure feed LPF and high-pressure feed HPF, both mixtures entered into a gap between an inner surface of the lid 43 b of the housing 43 and one side surface of the rotary member 46, which opposes the above-mentioned inner surface, in the internal space 41 of the case 43 a of the housing 43, function as a thrust bearing between the inner surface of the lid 43 b and the one side surface of the rotary member 46 with the rotation of the rotary member 46 on the outer circumferential surface of the other end portion of the center shaft 44. Simultaneously, the mixture of the low-pressure brine LPB and high-pressure brine HPB, entered into a gap between the end surface of the other end portion of the center shaft 44 and the bottom surface of the blind hole 46 a of the rotary member 46, function as a thrust bearing between the end surface of the other end portion of the center shaft 44 and the bottom surface of the blind hole 46 a of the rotary member 46 with the rotation of the rotary member 46 on the outer circumferential surface of the other end portion of the center shaft 44. Further, the mixture of the low-pressure feed LPF and high-pressure feed HPF, entered into a gap between the bottom surface of the internal space 41 of the case 43 a of the housing 43 and the other side surface of the rotary member 46, which opposes the above-mentioned bottom surface, in the internal space 41 of the case 42 a of the housing 43, functions as a thrust bearing between the bottom surface of the internal space 41 of the case 43 a and the other side surface of the rotary member 46 with the rotation with the rotation of the rotary member 46 on the outer circumferential surface of the other end portion of the center shaft 44.

Therefore, there is no need for independent thrust bearings between the inner surface of the lid 43 b and the one side surface of the rotary member 46, between the end surface of the other end portion of the center shaft 44, and between the bottom surface of the internal space 41 of the case 43 a and the other side surface of the rotary member 46, and it is possible to simplify the structure of the power recovery device 24′ of this embodiment and to reduce the manufacturing cost thereof.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms;

furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

What is claimed is:
 1. A power recovery device which is used in a liquid processing apparatus in which raw water as externally supplied water containing a plurality of components is supplied to a reverse osmosis membrane through a pressure raising unit and extracts a part of fresh water from the pressure raised raw water by the reverse osmosis membrane, and which supplies raw water a pressure of which is raised by using a pressure of remaining raw water from which the part of the fresh water is extracted by the reverse osmosis membrane to the reverse osmosis membrane, in addition to the pressure raised raw water from the pressure raising unit, the power recovery device comprising: a housing having an internal space; a center shaft fixed in the internal space of the housing and having an outer circumferential surface and at least one end portion protruding outside the housing; and a rotary member accommodated in the internal space of the housing such that the rotary member is rotatable on the outer circumferential surface of the center shaft, having an inner circumferential surface opposing the outer circumferential surface of the center shaft and an outer circumferential surface positioned outside the center shaft in a radial direction of the center shaft, and including a plurality of channels arranged at equal intervals in a circumferential direction of the center shaft and each extending between the inner circumferential surface thereof and the outer circumferential surface thereof, wherein at least one set of two pairs of chambers opposing the outer circumferential surface of the rotary member and divided from each other is provided in the internal space of the housing, at least one set of two pairs of openings opening in the outer circumferential surface of the center shaft to be equal in number to the chambers to oppose the at least one set of the chambers in the internal space of the housing through the rotary member, and at least one set of two pairs of passages extending through the center shaft from the at least one set of the openings and opening in the at least one end portion of the center shaft, are formed in the center shaft, one pair of the chambers symmetrically arranged with respect to the center shaft in the one set of the chambers in the internal space of the housing is configured to be introduced with the externally supplied raw water and to cause the externally supplied raw water to push the plurality of channels in the outer circumferential surface of the rotary member exposed in the one pair of chambers, in a predetermined circumferential direction of the outer circumferential surface so as to rotate the rotary member, the other pair of the chambers symmetrically arranged with respect to the center shaft in the one set of the chambers is connected to a channel of the pressure raised raw water between the pressure raising unit and the reverse osmosis membrane, one pair of the openings of the one set of openings in the outer circumferential surface of the center shaft, opposing the one pair of the chambers through the rotary member are communicated with an outside through one pair of the passages corresponding to the one pair of the openings in the center shaft, and the other pair of the openings of the one set of the openings in the outer circumferential surface of the center shaft, opposing the other pair of the chambers through the rotary member is introduced with the remaining raw water through the other pair of the passages corresponding to the other pair of the openings in the center shaft.
 2. The power recovery device according to claim 1, wherein the center shaft is long and narrow, and has another end portion protruding outside the housing in a side opposite to the one end portion along a longitudinal central line of the center shaft, the one pair of the passages of the center shaft opens in the one end portion of the center shaft, and the other pair of the passages of the center shaft opens in the other end portion of the center shaft.
 3. The power recovery device according to claim 1, wherein the center shaft is long and narrow, and has another end portion positioned in a side opposite to the one end portion along a longitudinal central line of the center shaft, and accommodated in the internal space of the housing.
 4. The power recovery device according to claim 1, further comprises an electric motor including an output shaft which is connected to the rotary member and rotates together with the rotary member.
 5. The power recovery device according to claim 1, wherein the raw water is salt water. 